On Tuesday, Sept. 11, 2001, Nick and Diane Marson were complete strangers who both happened to be on Continental Airlines flight C03. Nick, a British native, was leaving his home in London for a business trip in Houston, while Diane was returning to her native Texas after a family vacation in the U.K.

Then unspeakable tragedy struck. Terrorists flew two passenger jets into the World Trade Center in New York; another into the Pentagon, close to Washington, D.C.; and another in a field in Somerset County, Pennsylvania. In the immediate aftermath, planes were diverted to other airports; Diane and Nick’s plane was one of 38 diverted to Gander, Newfoundland.

About 30 hours after their plane landed — “We drank the plane dry,” Nick says of how passengers tried to cope with the uncertainty and fear — Nick and Diane were finally able to get off the aircraft. They were just two of the 6,700 passengers who suddenly descended on the small Canadian town with a population of 11,000.

As hospitable residents scrambled to house and feed the unexpected and anguished guests, Diane and Nick locked eyes while sheltering at the Society of United Fishermen Lodge 47 in Gambo.

“Is it all right if I take this bed?” asked Nick, motioning to the cot next to Diane. She said yes.

The duo, both single with grown children from previous marriages, immediately bonded while grappling with the tragedy, taking walks when the images on TV became too much to bear.

“Neither of us got on that plane looking for a romantic encounter,” Nick, 70, says in this week’s issue of PEOPLE. “That was the last thing on our minds.”

But at Dover Falls, Nick couldn’t help but snap a photo of Diane with his camera. “That’s when I knew he was interested in me and not the scenery,” says Diane, now 78, laughing.

Sparks flew again at a screeching event, where visitors must kiss a fish to become honorary Newfoundlanders. Looking at the friendly duo, the master of ceremonies first assumed they were married — and then, upon being corrected, offered to ordain the wedding. “She goes, ‘Why not?’ ” says Nick, beaming with a smile.

Though Diane insists she “said it in jest,” the moment led to their first kiss before they boarded their flight to the U.S. that Saturday, after the FAA reopened the American airspace.

For more on Nick and Diane Marson, pick up the latest issue of PEOPLE, on newsstands Friday

“I was upset,” admits Diane. “It was raining, we were leaving, and we’d just left these people we’d met.”

When Nick went to comfort Diane by kissing her on the forehead, “I figured he missed,” admits Diane, “so I just grabbed him and gave him a big smooch.”

“That changed the whole relationship right there,” Nick says.

“I thought, it’s now or never,” adds Diane, “and once we get back, we’ll never see each other again.”

But instead, her single smooch “lit a fire under me,” says Nick. “It’s like, good lord — I thought those days were over.”

Back in Texas, Nick and Diane “connected outside of Newfoundland” while Nick finished his work trip. After they parted ways, the new friends began emailing and talking on the phone before Nick returned to see Diane that October.

Then came the proposal: Nick says he popped the question during a call from his car in November. Following an “emotional roller-coaster” year where he traveled back and forth, he finally moved to Houston.

The beginnings of their romance are forever cemented in the documentary You Are Here (in theaters for the Sept. 11 anniversary) and the hit Broadway musical Come from Away, which the Marsons have seen 107 times.

“Why should this wonderful thing happen in the wake of disaster? It didn’t seem right,” says Diane, thinking about the 2,997 victims and their loved ones, including the “children who were born after their parents were killed in the World Trade Center.”

“I think it’s always in the back of my mind, because it didn’t seem right that we should have received this extra dose of happiness,” adds Nick. “So many people were suffering.”

But now, the couple sees a lesson in their love story: “In the darkest of circumstances, good things can still happen. The world is in turmoil, but don’t shut yourself away.”